Figure 3.

Conversion of HCC2998 and MKN45 cells to a more malignant, invasive type after expression of constitutively active PI 3-kinase. (a) Elevation of colony-forming efficiency in soft agar after expression of constitutively active PI 3-kinase. Three hundred cells of HCC2998/BD110 and MKN45/BD110 before and after induction of BD110 were embedded in a medium containing 0.4% agarose. After two weeks, the numbers of colonies over 0.5 mm in diameter were scored in two independent experiments each with duplicate dishes. (b) Representative colonies formed by active PI 3-kinase-expressing cells or their parental cells. (c) Constitutively active PI 3-kinase-expressing cells formed malignant, poorly differentiated carcinomas showing high invasiveness in nude mice. HCC2998/BD110 cells or MKN45/BD110 cells were transplanted into subcutaneous tissue of nude mice before or 40 days after the infection with AxCANCre. Cells without pBD110 expression preserved their intestinal cell nature and polarity as shown by the presence of papillary or tubular structures (arrowheads) with lumen (L, Upper), in which the presence of mucus was detected by the PAS reaction (data not shown). In contrast, the BD110-expressing cells (shown by arrows) in the tumors lost their polarity and proliferated diffusely in solid or trabecular patterns. Stromal fibroblasts proliferated among the cancer cells. The histological features of the xenotransplants are summarized in Table 1.